Hi All, I am planing for an Exchange HA soultion with 2 Mailbox Servers and 2 CAS+HUB Servers. How many exchange licenses i require? I think i need 2 licenses, as 1 license for Mailbox+CAS+HUB and 2nd for other Mailbox+CAS+HUB role. But they will be on different machines. Need your adivce on this.

Hello, when you separate the Mailbox servers and the CAS + HUB servers to different machines, you'll have 4 installations of Exchange and you'll need 4 licenses. Installing the CAS and HUB roles with MS load balancing on a DAG is not supported. But you can install CAS and HUB on the DAG if you have a hardware load balancer in place. In this case you'll need 2 licenses. And don't forget about the CALs for your clients! Greetings, Toni

Thanks for your swift response. Lets say i have 100 Clients in the same scenario, do i need 200 CALS 100 for each CAS role?

Hello, no, with 100 clients you'll just need 100 CALs but you have to separate if you need standard or enterprise CALs: http://www.microsoft.com/exchange/en-us/licensing-exchange-server-email.aspx Greetings, Toni